Exploring, drilling and completing hydrocarbon and other wells are generally complicated, time consuming and ultimately very expensive endeavors. As a result, over the years, well architecture has become more sophisticated where appropriate in order to help enhance access to underground hydrocarbon reserves. For example, as opposed to vertical wells of limited depth, it is not uncommon to find hydrocarbon wells exceeding 30,000 feet in depth which are often fairly deviated with horizontal sections aimed at targeting particular underground reserves.
In recognition of the potentially enormous expense of well completion, added emphasis has been placed on well monitoring and maintenance. That is, placing added emphasis on increasing the life and productivity of a given well may help ensure that the well provides a healthy return on the significant investment involved in its completion. Thus, over the years, well diagnostics and treatment have become more sophisticated and critical facets of managing well operations.
In the case of non-vertical (i.e. ‘horizontal’) wells as noted above, the more sophisticated architecture may increase the likelihood of accessing underground hydrocarbons. However, the nature of such wells presents particular challenges in terms of well access and management. For example, during the life of a well, a variety of well access applications may be performed within the well with a host of different tools or measurement devices. However, providing downhole access to wells of such challenging architecture may require more than simply dropping a wireline into the well with the applicable tool located at the end thereof. Rather, coiled tubing is frequently employed to provide access to wells of more sophisticated architecture.
Coiled tubing operations are particularly adept at providing access to highly deviated or tortuous wells where gravity alone fails to provide access to all regions of the wells. During a coiled tubing operation, a spool of pipe (i.e., a coiled tubing) with a downhole tool at the end thereof is slowly straightened and forcibly pushed into the well. This may be achieved by running coiled tubing from the spool, at a truck or large skid, through a gooseneck guide arm and injector which are positioned over the well at the oilfield. In this manner, forces necessary to drive the coiled tubing through the deviated well may be employed, thereby advancing the tool through the well.
Well diagnostic tools and treatment tools may be advanced and delivered via coiled tubing as described above. Diagnostic tools, often referred to as logging tools, may be employed to analyze the condition of the well and its surroundings. Such logging tools may come in handy for building an overall profile of the well in terms of formation characteristics, well fluid and flow information, etc. In the case of production logging, such a profile may be particularly beneficial in the face of an unintended or undesired event. For example, unintended loss of production may occur over time due to scale buildup or other factors. In such circumstances, a logging tool may be employed to determine an overall production profile of the well. With an overall production profile available, the contribution of various well segments may be understood. Thus, as described below, corrective maintenance in the form of a treatment application may be performed at an underperforming well segment based on the results of the described logging application. For example, in the case of scale buildup as noted above, an acidizing treatment may subsequently be employed at the location of the underperforming segment.
Unfortunately, in circumstances where an accurate production profile is obtained via coiled tubing as described above, the entire coiled tubing must be removed before a treatment application may ensue. Once more, due to the challenging architecture of the well, the treatment application is again achieved via coiled tubing. Thus, a separate coiled tubing assembly must generally be available at the well site for delivery of a treatment tool (e.g. for an acidizing treatment at an underperforming well segment). In addition to added capital expense, this will ultimately cost a significant amount of time. That is, substantial time is lost in terms of withdrawal of the initial coiled tubing and rigging-up the subsequent coiled tubing for treatment, not to mention the time incurred in actually running the treatment application. All in all, several hours to days are often lost due to the duplicitous nature of such coiled tubing deployments.
The apparent redundancy in repeated coiled tubing deployments as described above, is due to the functional equipment requirements of conventional logging tools. For example, the logging tool is much more than a mere pressure or temperature sensor. Rather it is an electrically powered device that is equipped for significant data acquisition and communication with hardware at the surface of the oilfield. Therefore, the delivery of such tools includes the advancement of an electrical cable that powers the tool, such as a conventional wireline cable that also communicatively tethers the tool to hardware at the oilfield surface.
As a result of the presence of a cable through the coiled tubing as noted above, treatment applications through the coiled tubing are generally impractical. That is, the substantial diameter of the cable relative that of the coiled tubing occludes the coiled tubing so as to limit flow, ballistic actuation (e.g. ‘ball drop’), and other features often employed in the subsequent treatment application. For example, a standard cable may be up to about 0.6 inches or more in diameter while disposed in coiled tubing having an inner diameter of generally less than about 2 inches. Furthermore, even in the case of low flow acidizing as noted above, the treatment itself is likely to damage the polymeric nature of the cable's outer layers. As a result, future communications with the logging tool would be impaired until the time and expense of cable replacement and/or repair were incurred. Thus, as a practical matter, coiled tubing logging applications generally remain followed by separately deployed coiled tubing treatment applications where necessary.